Consumers in Japan are unknowingly eating dolphin and porpoise-- marketed as whale meat--that contain dangerously high levels of mercury and other contaminants, according to new research by a Harvard University biologist.

The scientist who discovered the contamination feels so strongly about the health threat that he took the unusual step last week of writing a letter to top Japanese officials calling for public warnings and an immediate ban on sales of the contaminated meat.

"We believe that Japanese consumers are receiving inadequate and, in some cases, inaccurate information about the cetacean products they purchase. As a result, such consumers are unwittingly consuming highly contaminated and potentially dangerous cetacean products," wrote Harvard biology professor Stephen Palumbi along with a British and a Japanese researcher.

Japanese officials, however, called the data incomplete and said Wednesday they will take no immediate action.

"As far as we know, whale meat products on the Japanese market do not contain high levels of contaminants," said a spokesman from Japan's Far Sea Division of the Ministry of Agriculture, Forestry and Fisheries who would not disclose his name.

Whale meat is considered a delicacy in Japan, sold at $50 per pound. Although commercial whale hunting is banned under an international treaty, the Japanese are allowed to eat meat from one species--minke whales in the Antarctic--that are caught under permits for scientific research.

Palumbi, a geneticist who used DNA tests, found that more than half of the sampled meat that was sold and labeled as whale was actually dolphin, porpoise or an illegally caught species of whale. The research team bought 130 samples of whale meat at fish markets, stores and restaurants in six cities across Japan.

Japanese consumers who eat the mislabeled dolphin or porpoise face a 70% chance of ingesting at least one pollutant at a level considered unsafe for human consumption, Palumbi said. One sample of dolphin meat labeled as whale contained 500 times more mercury than Japan's health advisory limit. Mercury, a potent chemical that is fatal at high doses and can cause birth defects and neurological damage at lower levels, is especially risky for pregnant women and children.

The findings have not yet been published in a scientific journal, but, Palumbi said, "I didn't feel right sitting on this information and letting the long-term scientific publication process drag on. I would have felt awful if I waited, and then heard about some mother in Japan giving birth to a baby with developmental problems because she ate dolphin."

The findings could reignite a smoldering global battle over whales. The Japanese government is wary of any Western interference in whale issues because it has steadfastly tried to relax the treaty that bans commercial whale hunts.

In the United States, environmentalists said they were surprised by the results, noting that it is the first time meat sold at markets has been shown to be contaminated. They vowed to work with their Japanese counterparts to urge the Japanese government to issue health warnings.

"Those concentrations are much too high and certainly no pregnant woman or children should be eating this stuff. It's an important message for the government to get out," said Theo Colborn, a World Wildlife Fund scientist who specializes in contaminants.

The spokesman for the Japanese ministry said officials there will examine the data, adding that the information in the letter "was very much one-sided and incomplete."

Palumbi included detailed charts showing the levels of all chemicals found in the meat. The most contaminated dolphin meat, according to the study, contained more than 200 parts per million of mercury in the liver--an amount he called "dangerously contaminated." The amount considered safe by the Japanese government for human consumption is 0.4 ppm.

The researchers said they have seen an increase in recent years in the amount of dolphin meat sold in Japanese markets.

"An important first step would be to immediately ban the sale of contaminated products," Palumbi wrote in the letter to two Japanese ministries overseeing health and fisheries issues.

Palumbi and his co-researchers urged the government to launch an investigation of the food industry involving the mislabeling and distribution of whale meat. The genetic tests revealed that some of the meat is from blue, humpback and sperm whales, endangered species that are illegal to hunt or sell.

The Japanese ministry spokesman said the government does not consider it improper for a market to label dolphin meat as whale meat because they are similar species. Fishing of dolphins and porpoises is not restricted.

Palumbi, however, said the difference is important because dolphins, porpoises and other whales usually contain far larger concentrations of mercury and other contaminants than minke whales because they live in more polluted waters.

Environmental groups, fearing illegal hunting, have long fought to close the loophole in the International Whaling Commission treaty that allows minke whales to be killed by research vessels. Japan says commercial hunting of some species should be allowed because they are abundant.

Cetaceans are traditionally eaten in northeastern Japan and Hokkaido. Elsewhere they are not widely consumed, although some restaurants in Tokyo and other cities specialize in whale.

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Times staff writer Valerie Reitman in Tokyo contributed to this story.